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VOLODYMYR KLIMCHUK
Senior Python / API Engineer
Ukraine • Remote • Python • FastAPI • REST APIs • Asyncio • AWS • PostgreSQL • Docker

PROFESSIONAL SUMMARY
Senior Python backend engineer with hands-on experience designing and building production-grade APIs, distributed services,
asynchronous systems, and data-intensive applications. Strong expertise in Python, FastAPI, asyncio, aiohttp, REST, OpenAPI,
SQLAlchemy, PostgreSQL, Redis, MongoDB, RabbitMQ/Celery, Docker, AWS, Terraform, CI/CD, testing, observability, and Linux.
Experienced in microservice architecture, API design, authentication and authorization, scalable data processing, caching, queues,
rate limiting, performance optimization, and reliable cloud deployments. Comfortable owning backend systems end-to-end, from
architecture and implementation through testing, deployment, monitoring, and production troubleshooting.

TECHNICAL SKILLS
Python 3.x • FastAPI • aiohttp • asyncio • Pydantic • SQLAlchemy 2.0 • PostgreSQL • MongoDB • Redis • KeyDB • RabbitMQ •
Celery • REST • HTTP • OpenAPI • Swagger • JSON • JWT • OAuth 2.0 • API authentication • Microservices • Distributed Systems
• ETL • Data Pipelines • Apache Airflow • AWS • Terraform • Docker • Docker Compose • Kubernetes • Linux • Nginx • Git • CI/CD •
GitHub Actions • pytest • mypy • Ruff • Black • Alembic • Prometheus • Grafana • Loki • Sentry • k6 • autocannon • React •
TypeScript • Rust/Axum

PROFESSIONAL EXPERIENCE

Senior Python / Backend Engineer
Independent / Project-Based Engineering

Designed and implemented scalable Python backend systems using FastAPI, aiohttp, asyncio, Pydantic, SQLAlchemy,
PostgreSQL, Redis, MongoDB, RabbitMQ, and Celery.
Built RESTful APIs with clean resource modeling, API versioning, OpenAPI specifications, validation, pagination, filtering,
authentication, authorization, structured errors, and consistent response contracts.
Implemented asynchronous I/O and concurrency patterns with asyncio, connection pooling, background workers, queues,
timeouts, retries, idempotency, and graceful failure handling.
Designed microservice architectures with clear service boundaries, asynchronous messaging, independently deployable
components, and horizontal scaling.
Developed ETL and data-processing pipelines for large datasets, including extraction, transformation, validation, deduplication,
normalization, incremental processing, and loading.
Worked with Apache Airflow for DAG-based workflow orchestration, scheduling, retries, task dependencies, monitoring, and
data pipeline automation.
Built and deployed cloud-based services on AWS, working with API Gateway, ECS/EKS, Lambda, S3, SQS/SNS, RDS, IAM,
CloudWatch, networking, and containerized workloads.
Provisioned infrastructure using Terraform, including reusable infrastructure definitions, variables, environments, networking,
compute, databases, IAM, and deployment automation.
Implemented CI/CD pipelines with automated linting, type checking, unit/integration tests, Docker builds, migrations, and
deployment stages.
Used pytest for backend testing, including unit tests, integration tests, API tests, async test scenarios, mocks, fixtures, and
database-backed tests.
Implemented Redis caching, distributed state, rate limiting, locks, and short-lived authentication/session data to reduce
database load and improve latency.
Designed PostgreSQL schemas and optimized SQL queries using indexes, joins, aggregations, query plans, transactions, and
SQLAlchemy async sessions.
Worked with MongoDB at scale, including compound indexes, query optimization, aggregation, deduplication, and large-
document processing.
Volodymyr Klimchuk • Senior Python / API Engineer

Built high-throughput services and performed load testing with k6 and autocannon; achieved approximately 11K
requests/second in performance testing on a Rust/Axum API backed by MongoDB/KeyDB.
Implemented production observability using structured logging, Prometheus metrics, Grafana dashboards, Loki log aggregation,
Sentry error tracking, health checks, and application-level monitoring.
Containerized backend systems with Docker and Docker Compose and managed Linux-based deployments behind Nginx with
HTTPS, firewalling, Fail2Ban, and operational monitoring.

SELECTED PROJECTS

Parser / Intermediary / Publisher Microservice Platform
Designed a distributed processing architecture where FastAPI services communicate through REST APIs and RabbitMQ/Celery
queues.
Implemented asynchronous parsing, result persistence, job state management, retries, failure handling, and downstream
publishing.
Separated synchronous API responsibilities from CPU/I/O-heavy background processing to keep request latency predictable.

High-Performance Data API
Built a high-throughput API backed by MongoDB and KeyDB/Redis, handling 600K+ documents.
Implemented indexing, deduplication, normalization, SHA-256 identifiers, caching, explicit database/cache timeouts, and
asynchronous access patterns.
Load-tested endpoints with k6/autocannon and optimized the service for high concurrent request volumes.

Messaging & Multi-Account Backend Platform
Built asynchronous backend infrastructure for large-scale multi-account messaging workloads.
Implemented account/session state, authentication flows, Redis-backed coordination, worker processing, API endpoints, and
persistent session management.
Designed the architecture for horizontal scaling and high concurrency, with a target of 1,000–10,000 concurrent users.

CLOUD / DEVOPS
AWS • Terraform • Docker • Kubernetes • Docker Compose • Linux • Nginx • CI/CD • GitHub Actions • PostgreSQL/RDS • Redis •
S3 • SQS/SNS • API Gateway • ECS/EKS • Lambda • IAM • CloudWatch • Prometheus • Grafana • Loki • Sentry

ENGINEERING PRACTICES
Clean Architecture • SOLID • Dependency Injection • Type Hints • Code Review • Unit Testing • Integration Testing • TDD-oriented
development • API-first design • Idempotency • Retries • Timeouts • Rate Limiting • Caching • Database Transactions • Query
Optimization • Secure Secrets Management • Production Debugging • Performance Testing

EDUCATION
Computer Science / Information Technology

ADDITIONAL
Strong practical focus on backend engineering and API platforms. Comfortable working independently, taking ownership of
technical decisions, investigating production issues, optimizing existing systems, and learning unfamiliar technologies quickly.

Volodymyr Klimchuk • Senior Python / API Engineer